Method and tool for tuning closely coupled circuits



Nov. 29, 1949 E. A. JENSEN ET AL 2,489,645

METHOD AND TOOL FOR TUNING CLOSELY COUPLED CIRCUITS Filed June 3, 1947 INVENTORS. 5/1/22? Q W Y Patented Nov.- 29, 1949- METHOD AND 'roor. ron TUNING cLosnLr comm) omoorrs Evan-A. Jensen, Westchester, and William Wilkin- Ion, Chicago, Ill., assignors to United Air Lines, Inc., Chicago, 111., a corporation of Delaware Application June a, 1m, Serial No. 752,168

13 Claims. (01. 171- -119) This invention relates to methods and tools for tuning closely coupled transformers and similar circuits, and the invention has for an object the provision of improved methods of tuning and the provision of a simple and inexpensive tool for carrying out such tuning methods..

In the past, difiiculties have been encountered in tuning or adjusting closely coupled circuits, such as radio frequency circuits for example, without recourse to frequency modulated generators or to laborious methods and complicated apparatus not adapted to use in the field. Radio receivers employing closely coupled, tuned, in-' termediate and radio frequency transformers have heretofore been employed, in which one winding of the transformer was mounted for bodily movement away from the other winding so as to loosen the coupling between the windings and permit independent tuning of the primary and secondary circuits. Such arrangements, however, have not been free from objection, due to the expense and the design complications involved in providing movable windings, and accordingly it is a further object of this invention to provide a simple and reliable method for tuning closely, coupled circuits without requiring physical shifting of the primary of secondary windings, and to provide a tuning tool which may be readily employed in the field for quickly and accurately carrying out the tuning operation.

In carrying out the invention in one form, tuning of the closely coupled circuits is accomplished by first detuning one portion of the circuit so as to permit tuning of the other portion, then inserting into the field of the tuned portion an element formed of a material capable of absorbing energy at the operating frequency so as effectively to detune the previously tuned portion, whereby the previously detuned portion may be independently tuned. Upon removal of the detuning element, the first tuned portion is restored to its tuned condition, thus completing the tuning operation. in order quickly and accurately to carry out the tuning operation, a tuning tool is provided which comprises a shaft of suitable loss'producing or energy-=absorbing material adapted to be inserted into the field of one portion of the circuit for detuning the same, and one end of the shaft is provided with a bit adapted to engage an adjustable element of the other portion of the circuit to effect tuning thereof. fit its opposite end the shaft is preferably provided with an insulating handl whereby the body capacity of the user is prevented from affecting the circuit being tuned.

For a more complete understanding of the invention, reference should be had to the drawing,

- in which:

Fig. 1 is a perspective view of a preferred form of tuning tool embodying the present invention;

Fig. 2 is a somewhat diagrammatic view, partially in section, of the tuning tool in Fig. 1 associated with a closely coupled transformer for carrying out a tuning operation embodying the present invention;

Fig. 3 is a fragmentary view similar to Fig. 2, illustrating the association of the tuning tool and the transformer during another portion of the tuning operation; and

Fig. 4. is a diagrammatic representation of another type of closely coupled circuit adapted to be tuned in accordance with the present invention.

Referring now to the drawing, the tuning tool 9 shown in Fig. 1, which is intended for use in relatively low frequency circuits, consists of an insulated handle 10 from which extends a shaft H which is preferably formed of magnetic material and which may be secured to the handle it in any desired manner, as for example by a pin or rivet l2. Surrounding the shaft ii intermediate its ends is an insulating sleeve i3, and at its end remote from the handle ID the shaft H is provided with a bit portion 14 formed of nonmagnetic material, suitable rivets i5 serving to secure the bit on the shaft. At the opposite end of the handle 10 is an extending portion i6 which is provided with a transversely extending pin I! the purpose of which will be described hereinafter.

Referring now to Figs. 2 and 3, the closely coupled transformer there shown consists of a suitable primary winding 18 and a secondary winding IS, the windings being arranged in closely coupled axial relation on an insulating support or tube 20, the opposite ends of the tube extending through upper and lower supporting plates 2| which are connected together by rods 22. Disposed within the secondary winding I9 is a core member 23 mounted on a threaded stem 24 which extends through and threadedly engages a suitable nut, not shown, carried on the lower end plate 26, so that rotation of the stem 24 is effective to move the core 23 axially with respect to the secondary winding I9.

Disposed within the primary winding I8 is a hollow core 25 the upper end of which is reduced in diameter and threaded, as indicated by'the reference numeral 26, the threaded portion extending through a nut 21 secured to the upper end plate 2 l. The extending end of the threaded portion 26 is provided, as shown, with radially disposed notches 28 adapted to receive the pin II of the tuning tool, as shown best in Fig. 3.

In practicing the tuning method embodying the present invention to effect quick and accurate tuning of the transformer shown in Figs. 2 and 3, the tuning tool of Fig. l is preferably employed. The first step in carrying out the tuning method is to rotate the threaded stem 24 of the core 23 so as to withdraw the core 23 from the secondary winding l3 and thus effectively detune the sec-' ondary winding. 'I'hereupon the tuning tool 3 is applied to the upper end of the hollow core 25 of the primar winding I8, as shown in Fig. 3, the transverse pin ll of the tool engaging the slots 28 in the hollow core, whereupon the tool is eflective to rotate the hollow core so as to ad- Just it axially of the primary winding l3 until the primary circuit is tuned to the proper frequency.

After the primary circuit has thus been tuned, the tuning tool 9 is withdrawn and reversed so that the shaft ll of magnetic material may be inserted through the hollow core to the position shown in Fig. 2 and the bit It is caused to engage a suitable slot 30 in the core 23. With the tool in this position the magnetic shaft ll serves to detune the previously tuned primary winding l3, whereupon the secondary winding I9 may properly be tuned by rotating the tuning tool 9 so as to move the core 23 axially of the secondary winding l9 and thereby tune this winding to the proper frequency, After proper tuning of the secondary winding l9 has been achieved, the tuning tool may be withdrawn, whereupon the primary circuit is restored to its previously tuned condition, resulting in proper tuning of the closely coupled circuits.

Although the shaft ll of the tuning tool is formed of magnetic material for use with relatively low frequencies, it may, where high or ultra-high radio frecuencies are involved, be formed of non-magnetic and even non-metallic materials, the choice of material depending upon the frequency. For example, at very high frequencies in the neighborhood of 100 megacycles or higher, the shaft may be formed of a synthetic resin, such as Bakelite or any similar material, which is a poor dielectric at those frequencies. Insertion of a shaft formed of such material into the field of one of the tuned windings will be effective to absorb energy and thus change the "Q" of the circuit, or detune the circuit, so as to permit proper tuning of the other circuit. As used herein, the term "detuning is intended to define any change in the tuning or coupling of the circuit which is efi'ective to permit proper tuning of the associated circuit, and may include either lowering of the Q" of the circuit or shifting the resonant frequency of the circuit, or effectively de-coupling the circuit.

In Fig. 4 a closely coupled circuit is shown comprising the windings 3| and 32 which are arranged in closely coupled relation, the windings 3i and 32 having adjustable condensers 33 and 34, respectively, connected thereacross. As shown in Fig. 4, the respective condensers 33 and 34 are arranged axially of the winding of the opposite circuit, so that the adjusting element 35 of the condenser M is disposed substantially on the center line of the winding 3|, and the adjusting element 36 of the condenser 33 is disposed substantially on the center line of the winding 32. In order to tune the circuit of Fig. 4, it is necessary onl to insert the tuning tool first through the winding 3|, which effectively detunes the portion or the circuit including the winding 8|, and by engaging the bit II with the adjusting element 35, the circuit including the condenser 34 and the winding 32 may then be accurately tuned. The tuning operation may then be completed by withdrawing the tool from the winding 3| and inserting it through the winding 32 so as to detune the previously tuned circuit including the winding 32 while permitting engagement of the bit It with the adjusting member 36 whereby tuning of the circuit including the condenser 33 and the winding 3| may be accomplished.

It will be understood, of course. that in carrying out the methods of the present invention, it is not necessary that the particular type of tuning tool herein disclosed be employed so long as some energy-absorbing or loss-producing instrumen tality is employed which may be inserted into th field of one of the tuned circuits to detune t circuit during tuning of the other circuit.

While we have shown particular embodiments of our invention, it will be understood, of course, that we do not wish to be limited thereto since many modifications may be made, and we therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention;

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. The method of tuning a closely coupled circuit including a pair of tuneable portions which comprises detuning a first of said portions, maintaining said first portion detuned while tuning the second of said portions, inserting a loss-producing element into the field of an inductive component of said tuned second portion to detune said tuned second portion, tuning said first portion while maintaining said element in said field, and removing said element from said field.

2. The method of tuning a closely coupled circuit including a pair of tuneable portions which comprises detuning a first of said portions, maintaining said first portion detuned while tuning the second of said portions, inserting a lossproducing element into the field of an inductive component of said tuned second portion to detune said tuned second portion, manipulating said element to tune said first portion while maintaining said element in said field, and removing said element from said field.

3. The method of tuning a closely coupled circuit including a pair of tuneable portions which comprises detuning a first of said portions, maintaining said first portion detuned while tuning the second of said portions, inserting a lossproducing element into the field of an inductive component of said tuned second portion to detune said tuned second portion, engaging said element with a tuneable element of said first portion, manipulating said element to tune said first portion while maintaining said element in said field, and thereafter removing said element from said field.

4. The method of tuning a closely coupled transformer having tuned primary and secondary circuits which comprises detuning said secondary circuit, tuning said primary circuit while said secondary circuit is detuned, inserting a loss-producing element into the field of the tuned primary winding to detune said primary circuit, tuning said secondary circuit while maintaining said element in said field, and removing said element from .said field to restore said primary circuit to its tuned ondition.

5. The method of tuning a closely coupled transformer having tuned primary and secondary circuits which comprises detuning said secondary circuit, tuning said primary circuit while said secondary circuit is detuned, inserting a magnetic element into the field of the tuned primary winding to detune said primary circuit, tuning said secondary circuit while maintaining said magnetic element in said field, and removing said nagnetic element from said field to restore said primary circuit to its tuned condition.

6. The method of tuning a closely coupled transformer having tuned primary and secondtry circuits which comprises inserting a loss-prolucing element into the field of the secondary winding to detune said secondary circuit, tuning said primary circuit while maintaining said element in said field, transferring said element from said field to the field of the primary winding temporarily to detune said tuned primary circuit, tun-' ing said secondary circuit while maintaining said element in said primary field, and removing said element to restore said primary circuit to its tuned condition.

7. The method of tuning a closely coupled transformer having tuned primary and secondary circuits which comprises inserting a magnetic element into the field of the secondary windin to detune said secondary circuit, tuning said primary circuit while maintaining said magnetic element in said field, transferring said magnetic element from said field to the field of the primary winding temporarily to detune said tuned primary circuit, tuning said secondary circuit while main-J taining said element in said primary field, and removing said element to restore said primary circuit to its tuned condition.

8. In a method of tuning a closely coupled circult, the step which consists of inserting a lossproducing element into the field of one tuned portion to detune the same while tuning the other portion of the circuit.

9. In a method of tuning a closely coupled transformer having-tuned primary and secondary windings, the step whichconsists of inserting a loss-producing element into the field of one of said windings to detune the sameduring tuning of the other winding.

10. A tool for tuning closely coupled circuit! of absorbing energy when inserted into a field at the circuit frequency, a bit on one end of said shaft formed of material which is nonabsorbing at said frequency, and a handle of insulating material on the opposite end of said shaft.

11. A tool for tuning closely coupled circuits comprising a shaft formed of magnetic material, a bit of non-magnetic material on one end of said shaft, and a handle of insulating material on the opposite end of said shaft.

12. A tool for tuning closely coupled circuits comprising a shaft of magnetic material adapted to be inserted into the field of one portion of the circuit for detuning the same, a bit of non-magnetic material on one end of said shaft for engaging an adjustable element of another portion of the circuit for tuning the same while said shaft is disposed in said field, and an insulating handle core portion.

comprising a shaft formed of a material capable on the other end of said shaft for minimizing the effect on said circuit of the body-capacity 0f the user.

13. A tool for tuning a closely coupled transformer of the type including axially aligned pri. mary and secondary coils, each coil containing therewithin an axially adjustable magnetic core for tuning the coil and one of said core portions being hollow, said tool comprising a shaft of magnetic material adapted to be inserted axially through said hollow core to detune one of said windings, a non-magnetic bit on one end of said shaft for engaging the other core portion to adjust the same, an insulating handle on said shaft remote from said bit, and means extending outwardly from said handle at the end opposite from said shaft for engaging said hollow core portion upon reversal of said tool to adjust said hollow EVAN a menu. wnmu wnmson.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS gasses Jacob Apr. 11, 1944 

